The heart is a muscular organ that pumps blood continuously throughout the body. It is comprised of four chambers — the right and left atrium and the right and left ventricle.

The four chambers of the heart work together by alternately contracting and relaxing to pump blood throughout the heart. To accomplish this, the heart uses an electrical system to trigger a heartbeat. Essentially, the electrical system is the power source that makes all the heart's functions possible.

Blood vessels lead in and out of the chambers, which receive and distribute blood throughout the body. The four chambers of the heart are connected by four valves — the tricuspid, pulmonic, mitral and aortic valves. These valves work like one-way doors, allowing blood to flow in only one direction.

Blood Circulation

Heart diagram showing blood circulationAs the heart beats, it pumps blood through a system of blood vessels called the circulatory system. The blood that these vessels carry is essential for the body to function. Blood carries oxygen and nutrients to your body's tissues, assists in the removal of carbon dioxide and waste products and promotes the overall health of the body's tissues. There are three main types of vessels that make up this system:

  • Arteries
  • Veins
  • Capillaries

How blood flow works

Blood enters the heart through two large veins, the inferior and superior vena cava, emptying into the right atrium. It flows from the right atrium through the tricuspid valve into the right ventricle. The right ventricle pumps blood to the pulmonic valve, and the blood flows into the pulmonary artery and to the lungs. Oxygenated blood returns from the lungs to the heart via the pulmonary vein into the left atrium. From the left atrium, blood flows through the mitral valve to the left ventricle. From the left ventricle blood leaves the heart through the aortic valve and flows into the aorta and to the body.

Coronary Arteries

Heart diagram of coronary artery functionThe heart muscle needs its own supply of oxygen and nutrients to pump properly. Although its chambers are full of blood, the heart receives no nourishment from this blood. The heart receives its own supply of blood through a network of arteries of the body known as the coronary arteries.

Functions of right and left coronary arteries

The coronary arteries wrap around the surface of the heart. The two main coronary arteries, the right coronary artery and the left coronary artery, branch off from the aorta. The right coronary artery supplies the right atrium and right ventricle. It branches into the posterior descending artery. The left coronary artery branches into the circumflex artery and the left anterior descending artery. The left coronary artery supplies the left atrium and the left ventricle.

Narrow coronary arteries

Collateral circulation is a network of tiny blood vessels that usually remain inactive. When coronary arteries narrow to the point that blood flow to the heart is limited, collateral vessels become enlarged and active. This process allows for blood flow around the blocked artery to the heart muscle.

Our Cardiovascular Program continues to receive recognition as one of the top programs nationally. We are honored to provide high-quality, effective care for even the most high-risk patients.

  • In its 2024 Specialty Excellence Awards, Healthgrades recognized Froedtert Hospital as one of America’s 50 Best Hospitals for Cardiac Surgery, one of America’s 100 Best Hospitals for Cardiac Care and one of America’s 100 Best Hospitals for Coronary Intervention, as well as other specialty achievements in various areas.

    Froedtert Hospital was named one of the nation’s 50 Top Cardiovascular Hospitals™ by Fortune and PINC AI™. Froedtert Hospital demonstrated significantly higher survival rates associated with cardiac care, with fewer readmissions and complications. To select top performers, an objective, independent, quantitative research analysis was performed using publicly available data measuring cardiac care in the U.S. Those in the top 50 operated at a lower cost and had better outcomes, had significantly higher inpatient survival rates, fewer patients with complications, lower readmission rates and spent up to $5,076 less in total costs per patient case. If all hospitals operated at the level of the top 50, there would be 7,600 fewer deaths due to heart disease, 6,700 fewer patients with complications and more than $1 billion saved each year, according to the analysis.

    The Society for Vascular Surgery's Vascular Quality Initiative (SVS VQI) has awarded Froedtert Hospital three out of three stars for its active participation in the Registry Participation Program. The mission of the SVS VQI is to improve patient safety and the quality of vascular care delivery by providing web-based collection, aggregation and analysis of clinical data submitted in registry format for all patients undergoing specific vascular treatments. The VQI operates 14 vascular registries.

    The American Heart Association recognized Froedtert Hospital with its Get With the Guidelines® Heart Failure Gold Plus Award. In addition, the hospital was recognized on the AHA’s Target: Heart Failure(SM) Honor Roll and received the AHA’s Target: Type 2 Diabetes Honor Roll™ award. 

    The American Heart Association also recognized Froedtert Hospital with its Get With the Guidelines® — Coronary Artery Disease Mission: Lifeline STEMI Receiving Silver Plus and Mission: Lifeline NSTEMI Silver awards. These awards demonstrate our commitment to improving care by adhering to the latest treatment guidelines and streamlining processes to ensure timely and proper care for heart attacks.

    The American Heart Association recognized Froedtert Hospital with its Get With the Guidelines® AFib Gold Award.

    ​The Cardiovascular Intensive Care Unit (CVICU) and Neurosurgical Intensive Care Unit (NICU) at Froedtert Hospital have each received a silver-level Beacon Award for Excellence from the American Association of Critical-Care Nurses. This award recognizes unit caregivers who successfully improve patient outcomes and align practices with AACN’s six Healthy Work Environment Standards. Receiving this national three-year award with gold, silver and bronze designations, marks a significant milestone on the path to exceptional patient care and achieving a healthy work environment.